A mail-handling machine equipped with a dimensional rating capability is already known, e.g. from U.S. Pat. No. 6,006,210 (Pitney Bowes).
That machine provides actual measurement of the height of the mail item by means of a strip of diodes. However, that apparently simple solution is extremely costly in practice. It assumes the use both of a very long strip and also of means for guaranteeing that the mail item is properly aligned or “jogged”, i.e. that it is not skew relative to the reference face of the machine.
In practice, unless other generally complex positioning devices are also used, mail items are often skew, and the amplitude of the skew depends on the type of the machine and on the type of item being conveyed.
U.S. Pat. No. 6,169,978 (Siemens) discloses a sophisticated system for determining the dimensions of the item being conveyed in order to assign a precise postage amount to it. That system also assumes that all of the items conveyed are positioned properly relative to a reference. Otherwise, the dimensional measurements are erroneous, and so are the postage amounts.